A plurality of infinitely variable change-speed gearboxes are known from the prior art, said gearboxes being composed of a combination of an infinitely variable variator and a change-speed gearbox in order to provide a sufficient adjustment range, and in which gearboxes the gearshifting elements are shifted with an approximately synchronous rotational speed. In this context, the gearboxes are shifted on the one hand by means of frictionally locking clutch elements (multi-plate clutches) and on the other hand by means of positively locking clutch elements (claw clutches). In these gearboxes, all the shifting points also have a disengaged or decoupled position (neutral) in addition to the engaged or coupled position, no torque being transmitted via the shifting point in said neutral position, in order to activate the clutch elements, all the gearboxes use hydraulic systems which are implemented, for example, by ring cylinders which are entrained in rotation, the oil for activation being fed via rotary bushings.
In gearboxes with shifting points with synchronous rotational speeds is particularly important, in order to bring about jolt-free operation, for the gearshifting process to take place at the correct/suitable time and at the same time for there to be neither an interruption in the force transfer (gearshifting hole) nor blockage of the gearbox in which both gearshifting elements of the synchronous shifting point are activated simultaneously.
The hydraulic actuators of a gearbox shifting point, which are used in the prior art, have shifting times of the order of magnitude of 100 ms and more. In addition, the shifting times are dependent on the oil pressure, the oil temperature and the oil viscosity, and, in the case of the rotating cylinders, they are also dependent on the rotational speed of the cylinder. In other words, the shifting times of a gearbox shifting point which is known from the prior art therefore vary. In addition, the shifting times change in an unpredictable way if a clutch cylinder cannot reach its end positions between two shifting operations which follow one another in brief succession.